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  <div class="section" id="module-stringprep">
<span id="stringprep-internet-string-preparation"></span><h1>6.6. <a class="reference internal" href="#module-stringprep" title="stringprep: String preparation, as per RFC 3453"><tt class="xref py py-mod docutils literal"><span class="pre">stringprep</span></tt></a> &#8212; Internet String Preparation<a class="headerlink" href="#module-stringprep" title="Permalink to this headline">¶</a></h1>
<p>When identifying things (such as host names) in the internet, it is often
necessary to compare such identifications for &#8220;equality&#8221;. Exactly how this
comparison is executed may depend on the application domain, e.g. whether it
should be case-insensitive or not. It may be also necessary to restrict the
possible identifications, to allow only identifications consisting of
&#8220;printable&#8221; characters.</p>
<p><span class="target" id="index-0"></span><a class="rfc reference external" href="http://tools.ietf.org/html/rfc3454.html"><strong>RFC 3454</strong></a> defines a procedure for &#8220;preparing&#8221; Unicode strings in internet
protocols. Before passing strings onto the wire, they are processed with the
preparation procedure, after which they have a certain normalized form. The RFC
defines a set of tables, which can be combined into profiles. Each profile must
define which tables it uses, and what other optional parts of the <tt class="docutils literal"><span class="pre">stringprep</span></tt>
procedure are part of the profile. One example of a <tt class="docutils literal"><span class="pre">stringprep</span></tt> profile is
<tt class="docutils literal"><span class="pre">nameprep</span></tt>, which is used for internationalized domain names.</p>
<p>The module <a class="reference internal" href="#module-stringprep" title="stringprep: String preparation, as per RFC 3453"><tt class="xref py py-mod docutils literal"><span class="pre">stringprep</span></tt></a> only exposes the tables from RFC 3454. As these
tables would be very large to represent them as dictionaries or lists, the
module uses the Unicode character database internally. The module source code
itself was generated using the <tt class="docutils literal"><span class="pre">mkstringprep.py</span></tt> utility.</p>
<p>As a result, these tables are exposed as functions, not as data structures.
There are two kinds of tables in the RFC: sets and mappings. For a set,
<a class="reference internal" href="#module-stringprep" title="stringprep: String preparation, as per RFC 3453"><tt class="xref py py-mod docutils literal"><span class="pre">stringprep</span></tt></a> provides the &#8220;characteristic function&#8221;, i.e. a function that
returns true if the parameter is part of the set. For mappings, it provides the
mapping function: given the key, it returns the associated value. Below is a
list of all functions available in the module.</p>
<dl class="function">
<dt id="stringprep.in_table_a1">
<tt class="descclassname">stringprep.</tt><tt class="descname">in_table_a1</tt><big>(</big><em>code</em><big>)</big><a class="headerlink" href="#stringprep.in_table_a1" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableA.1 (Unassigned code points in Unicode 3.2).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_b1">
<tt class="descclassname">stringprep.</tt><tt class="descname">in_table_b1</tt><big>(</big><em>code</em><big>)</big><a class="headerlink" href="#stringprep.in_table_b1" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableB.1 (Commonly mapped to nothing).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.map_table_b2">
<tt class="descclassname">stringprep.</tt><tt class="descname">map_table_b2</tt><big>(</big><em>code</em><big>)</big><a class="headerlink" href="#stringprep.map_table_b2" title="Permalink to this definition">¶</a></dt>
<dd><p>Return the mapped value for <em>code</em> according to tableB.2 (Mapping for
case-folding used with NFKC).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.map_table_b3">
<tt class="descclassname">stringprep.</tt><tt class="descname">map_table_b3</tt><big>(</big><em>code</em><big>)</big><a class="headerlink" href="#stringprep.map_table_b3" title="Permalink to this definition">¶</a></dt>
<dd><p>Return the mapped value for <em>code</em> according to tableB.3 (Mapping for
case-folding used with no normalization).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_c11">
<tt class="descclassname">stringprep.</tt><tt class="descname">in_table_c11</tt><big>(</big><em>code</em><big>)</big><a class="headerlink" href="#stringprep.in_table_c11" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableC.1.1  (ASCII space characters).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_c12">
<tt class="descclassname">stringprep.</tt><tt class="descname">in_table_c12</tt><big>(</big><em>code</em><big>)</big><a class="headerlink" href="#stringprep.in_table_c12" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableC.1.2  (Non-ASCII space characters).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_c11_c12">
<tt class="descclassname">stringprep.</tt><tt class="descname">in_table_c11_c12</tt><big>(</big><em>code</em><big>)</big><a class="headerlink" href="#stringprep.in_table_c11_c12" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableC.1  (Space characters, union of C.1.1 and
C.1.2).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_c21">
<tt class="descclassname">stringprep.</tt><tt class="descname">in_table_c21</tt><big>(</big><em>code</em><big>)</big><a class="headerlink" href="#stringprep.in_table_c21" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableC.2.1  (ASCII control characters).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_c22">
<tt class="descclassname">stringprep.</tt><tt class="descname">in_table_c22</tt><big>(</big><em>code</em><big>)</big><a class="headerlink" href="#stringprep.in_table_c22" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableC.2.2  (Non-ASCII control characters).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_c21_c22">
<tt class="descclassname">stringprep.</tt><tt class="descname">in_table_c21_c22</tt><big>(</big><em>code</em><big>)</big><a class="headerlink" href="#stringprep.in_table_c21_c22" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableC.2  (Control characters, union of C.2.1 and
C.2.2).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_c3">
<tt class="descclassname">stringprep.</tt><tt class="descname">in_table_c3</tt><big>(</big><em>code</em><big>)</big><a class="headerlink" href="#stringprep.in_table_c3" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableC.3  (Private use).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_c4">
<tt class="descclassname">stringprep.</tt><tt class="descname">in_table_c4</tt><big>(</big><em>code</em><big>)</big><a class="headerlink" href="#stringprep.in_table_c4" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableC.4  (Non-character code points).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_c5">
<tt class="descclassname">stringprep.</tt><tt class="descname">in_table_c5</tt><big>(</big><em>code</em><big>)</big><a class="headerlink" href="#stringprep.in_table_c5" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableC.5  (Surrogate codes).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_c6">
<tt class="descclassname">stringprep.</tt><tt class="descname">in_table_c6</tt><big>(</big><em>code</em><big>)</big><a class="headerlink" href="#stringprep.in_table_c6" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableC.6  (Inappropriate for plain text).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_c7">
<tt class="descclassname">stringprep.</tt><tt class="descname">in_table_c7</tt><big>(</big><em>code</em><big>)</big><a class="headerlink" href="#stringprep.in_table_c7" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableC.7  (Inappropriate for canonical
representation).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_c8">
<tt class="descclassname">stringprep.</tt><tt class="descname">in_table_c8</tt><big>(</big><em>code</em><big>)</big><a class="headerlink" href="#stringprep.in_table_c8" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableC.8  (Change display properties or are
deprecated).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_c9">
<tt class="descclassname">stringprep.</tt><tt class="descname">in_table_c9</tt><big>(</big><em>code</em><big>)</big><a class="headerlink" href="#stringprep.in_table_c9" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableC.9  (Tagging characters).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_d1">
<tt class="descclassname">stringprep.</tt><tt class="descname">in_table_d1</tt><big>(</big><em>code</em><big>)</big><a class="headerlink" href="#stringprep.in_table_d1" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableD.1  (Characters with bidirectional property
&#8220;R&#8221; or &#8220;AL&#8221;).</p>
</dd></dl>

<dl class="function">
<dt id="stringprep.in_table_d2">
<tt class="descclassname">stringprep.</tt><tt class="descname">in_table_d2</tt><big>(</big><em>code</em><big>)</big><a class="headerlink" href="#stringprep.in_table_d2" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine whether <em>code</em> is in tableD.2  (Characters with bidirectional property
&#8220;L&#8221;).</p>
</dd></dl>

</div>


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